Photoconductive elements containing haloarylketone-formaldehyde polymeric binders

ABSTRACT

PHOTOCONDUCTIVE ELEMENTS CONTAINING A PHOTOCONDUCTOR AND BINDER FOR THE PHOTOCONDUCTOR COMPRISING A HALOARYL-KETONE-FORMALDEHYDE RESIN ARE DESCRIBED. THE DESCRIBED ELEMENTS CAN BE SENSITIZED AND CHARGE EITHER NEGATIVELY OR POSITIVELY AND USED TO PREPARE IMAGES ELECTROPHOTOGRAPHICALLY.

United States Patent 17 Claims ABSTRACT OF THE DISCLOSURE'Photoconductive elements containing a photoconductor and binder for thephotoconductor comprising a haloaryl-ketone-formaldehyde resin aredescribed. The described elements can be sensitized and charged eithernegatively or positively and used to prepare imageselectrophotographically.

This invention relates to novel electrophotographic elements havingcoatings of binder-containing photoconductive compositions.

Binder-containing photoconductive compositions have been widely used inthe preparation of electrophotographic elements. In electrophotographicreproduction process, these elements are utilized in the formation oflatent electrostatic images. In some applications the photoconductivecompositions contain an organic photoconductor and a sensitizeduniformly admixed in an inert resinous binder. Many binders arecurrently used in connection with a wide variety of available organicphotoconductor compounds and compositions. Typical binders are ordinarypolymeric materials, e.g., phenolic resins, acrylic ester resins,polystyrene, etc. However, these binders usually do not impart anyparticular improvement in light sensitivity to the system. The lightsensitivity as indicated by the electrical speed of these particularsystems is ordinarily due wholly to the organic photoconductor andsensitizer. Other binders have been found to contribute significantly tothe light sensitivity of the system. However, the selection of thesepolymers for incorporation into photoconductive compositions to formelectrophotographic layers has proceeded on a compound-by-compoundbasis. Nothing has yet been discovered from the numerous binders testedwhich permite effective prediction and selection of particular polymersexhibiting the desired properties.

It is, therefore an object of this invention to provide improved novelbinder-containing photoconductive compositions which exhibit high lightsensitivities. I

It is another object to provide transparent electrophotographic elementshaving the high speed characteristic of the novel photoconductivecompositions of this invention.

It is a further oject of this invention to provide a reproductionprocess for using electrophotographic elements containing the novelbinders of this invention.

These and other objects of this invention are accomplished by using anelectrophotographic element having coated thereon a photoconductivecomposition which contains a photoconductor admixed with a binder whichis a halorylketone-formaldehyde resin.

It has been discovered that such compositions exhibit increased lightsensitivities as evidence by greater electrical speeds. In particular,substantial increases in speeds are obtained as compared to speedsattainable with many other closely related polymeric bindercompositions, including those arylketone-formaldehyde resins whichcontain no halogen. These increases in speed are observed when thecoating accepts a suitable potential (e.g'( 500- 600 volts) and therelative speed of the coating is determined on the basis of thereciprocal of the exposure required to reduce the potential of thesurface charge by volts (shoulder speed) or to 100 volts (toe speed).The terms shoulder speed and to speed are terms known in the silverhalide photographic art with reference to H and D curves. As usedherein, such terms refer to related curves resulting from exposureplotted against voltage. The reduction of the surface potential to 100volts or below is significant in that it represents a requirement forsuitable broad area development of an electrostatic image. The realtivespeed at 100 volts is a meaure of the ability to produce and henceforthto develop or otherwise utilize the electrostatic latent image. When thephotoconductor is absent from the coating and only a conventional binderis used, the surface potential does not drop to or below 100 vots andtherefore no speed can be assigned to such a composition. When aphotoconductor is part of the coating in many conventional polymericbinders, the surface potentials of such resultant compositions usuallydrop below 100 volts, and thus, a definite speed can be ascertained.However, these speeds are improved when the binders of this inventionare employed.

The aryl nucleus of the novel haloarylketone-formaldehyde resinousbinders of this invention is substituted in either the ortho, meta orpara position (with respect to the -carboyl grouping) by any of thehalogens including chlorine, bromine, iodine and fluorine. The arylnucleus can contain further substitution including one or moreadditional halogen atoms, an alkyl group having 1 to 10 carbon atomsincluding an aliphatic alkyl group as well as a cycloalkyl group, anaryl group such as phenyl or naphthyl, an amino group including asubstituted amino group such as dialkylamino group, a hydroxy group,etc. Binders comprising such polymers improve the electrical speed ofthe phtoconductive composition.

Particularly useful binders of this invention comprise polymers whichcontain the repeating unit wherein X is a halo-substituted aryl groupsuch as halophenyl,

halonaphthyl, etc., e.g., p-chlorophenyl, 3,4-dichlorophenyl,3-methyl-4-chlorophenyl, 3-phenyl-4-bromophenyl, 3 diethylamino 4bromophenyl, 3 chloro 4 hydroxyphenyl, 3 cyclohexyl 4 chlorophenyl, and

R is either (1) an alkyl group having 1 to 4 carbon atoms includingsubstituted alkyl groups such as haloalkyl, aralkyl, etc., e.g., methyl,ethyl, propyl, butyl, isopropyl, chloromethyl, trifluoromethyl, benzyl,cyclobutyl, etc., (2) hydrogen or (3) an aryl radical including asubstituted aryl radical such as alkaryl, haloaryl, etc., e.g., phenyl,naphthyl, bromophenyl, tolyl, dichloronaphthyl, trimethylphenyl, etc.

Exemplary of a few of the many resins useful as binders in thisinvention are listed in the following table.

(1) p-Bromoacetophenone-formaldehyde resin (2)p-Fluoroacetophenone-formaldehyde resin (3)m-Chloroacetophenone-formaldehyde resin (4)p-Chloroacetophenone-formaldehyde resin (5m-Iodoacetophenone-formaldehyde resin (6)3',4-dichloroacetophenone-formaldehyde resin (7)p-Bromopropionphenoneformaldehyde resin (8)1-acetyl-4-bromonaphthalene-formaldehyde resin (9)3'-diethylamino-4'-bromoacetophenone-formaldehide resin (10)3'-cyclohexyl-4'-chloroacetophenone-formaldehyde resin l l)3'-bromo-4'-phenylacetophenone-formaldehyde resin (12)p-Bromobutyrophenone-formaldehyde resin 13) Z-(p-bromophenyl)-4'-bromoacetophenone-formaldehyde resin (14)4-(p-bromophenyl)-4'-bromobutyrophenone-formaldehyde resin In preparingtypical electrophotographic elements utilizing the polymeric binders ofthis invention, a photoconductor is dissolved in a solution of binderand solvent and then, after thorough mixing, the composition is coatedon an electrically conducting support in a well-known manner, such asswirling, spraying, doctor blade coating, and the like.

The novel binders of this invention improve the electrical speeds ofcompositions containing a wide variety of photoconductors includinginorganic photoconductors such as zinc oxide, titanium dioxide, cadmiumsulfide and the like and organic photoconductors includingorganometallic photoconductors.

Typical photoconductors useful with the binders of this invention aredescribed below.

(A) Arylamine photoconductors including substituted and unsubstitutedarylamines, diarylamines, nonpolymeric triarylamines and polymerictriarylamines such as those described in US. Pats. 3,240,597 and3,180,730.

(B) Photoconductors represented by the forumla wherein Z represents anononuclear or polynuclear divalent aromatic radical, either fused orlinear (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or asubstituted divalent aromatic radical of these types wherein saidsubstituent can comprise a member such as an acyl group having from 1 toabout 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkylgroup having from 1 to about 6 carbon atoms (e.g., methyl, ethyl,propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbonatoms (e.g., methoxy, ethoxy, propoxy, pentoxy, etc.), or a nitro group;Z represents a mononuclear or polynuclear monovalent or polynuclearmonovalent aromatic radical, either fused or linear (e.g., phenyl,naphthyl, biphenyl, etc.); or a substituted monovalent aromatic radicalwherein said substituent can comprise a member, such as an acyl grouphaving from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl,etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g.,methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 toabout 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitrogroup; Q can represent a hydrogen atom or an aromatic amino group, suchas ZNH; b represents an integer from 1 to about 12, and L represents ahydrogen atom, a mononuclear or polynuclear aromatic radical, eitherfused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substitutedaromatic radical wherein said substituent comprises an alkyl group, analkoxy group, an acyl group, or a nitro group, or a poly(4'-vinylphenyl)group which is bonded to the nitrogen atom by a carbon atom of thephenyl group, these materials being more fully described in US. Pat.3,265,496.

(C) Polyarylalkane photoconductors including leuco bases of diaryl ortriarylmethane dye salts, 1,1,1-triarylalkanes wherein the alkane moietyhas at least two carbon atoms and tetraarylmethanes having an aminogroup substituted in at least one of the aryl nuclei attached to thealkane and methane moieties of the latter two classes of photoconductorswhich are non-leuco base materials; and also other polyarylalkanesincluded by the formula:

wherein each of D, E and G is an aryl group and J is a hydrogen atom, analkyl group, or an aryl group, at least one of D, E and G containing anamino substituent, the aryl groups attached to the central carbon atombeing preferably phenyl groups, although naphthyl groups can also beused including substituted aryl groups containing substituents such asalkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy, halogen,etc. in the ortho, meta or para positions, ortho-substituted phenylbeing preferred; the aryl groups can also be jointed together orcyclized to form a fiuoroene moiety, for example; the amino substituentcan be represented by the formula wherein each R can be an alkyl grouptypically having 1 to 8 carbon atoms, a hydrogen atom, an aryl group, ortogether the necessary atoms to form a heterocyclic amino grouptypically having 5 to 6 atoms in the ring such as moropholino, pyridyl,pyrryl, etc.; at least one of D, E and G preferably being ap-dialkylaminophenyl group, when I is an alkyl group, such an alkylgroup more generally has 1 to 7 carbon atoms, these materials being morefully described in US. Pat. 3,274,000, French Pat. 1,383,461 and in US.Ser. No. 627,857, filed Apr. 3, 1967 by Seus and Goldman.

(D) Photoconductors comprising 4-diarylamino-substituted chalconeshaving the formula:

wherein R and R are each phenyl radicals including substituted phenylradicals, R preferably having the formula wherein R and R are each arylradicals, aliphatic residues of l to 12 carbon atoms such as alkylradicals preferably having 1 to 4 carbon atoms, or hydrogen;particularly advantageous results being obtained when R is a phenylradical including a substituted phenyl radical and where R isdiphenylaminophenyh, dimethylaminophenyl or phenyl, these materialsbeing more fully described in Fox application U.S. Ser. No. 613,846.

(E) Non-ionic cycloheptenyl compounds which may be substituted withsubstituents such as ,(a) an aryl radical including substituted as wellas unsubstituted aryl radicals, (b) a hydroxy radical, (c) an azidoradical, (d) a heterocyclic radical having 5 to 6 atoms in theheterocyclic nucleus and at least one hetero nitrogen atom, andincluding substituted and unsubstituted heterocyclic radicals, and (e)an oxygen linked cycloheptenyl moiety. The substitution on thecycloheptenyl nucleus occurs at an unsaturated carbon atom when thecycloheptenyl moiety is a conjugated triene with no aromatic structurefused thereto. However, if there is at least one aromatic structure tothe cycloheptenyl moiety, then the substituents are attached to asaturated carbon atom. Additional photoconductors within this class areincluded in one of the following formulae:

where E and G can be either:

(a) a phenyl radical, (b) a naphthyl radical.

(c) a heterocyclic radical having to 6 atoms in the heterocyclic nucleusand at least one hetero nitrogen atom,

(d) a hydroxyl radical, or p ,(e) an oxygen containing radical having astructure such that the resultant cycloheptenyl compopnd is asymmetrical ether;

D can be any of the substituents defined for E and 6,, above and isattached to a carbon atom in the cycloheptenyl nucleus having a doublebond; (R and R (R and R (R and R and (R and R are together the necessaryatoms to complete a benzene ring fused to the cycloheptenyl nucleus;these compounds being more fully described in U.S. Ser. No. 654,091filed July 18, 1967.

(F) Compounds containing an NN nucleus including (1) unsubstituted andsubstituted N,N-bicarbazolyls containing substituents in either or bothcarbazolyl nuclei such as (a) an alkyl radical including a substitutedalkyl radical such as a haloalkyl or an alkoxyalkyl radical,

(b) a phenyl radical including a substituted phenyl radical such as anaphthyl, an aminophenyl or a hydroxyphenyl radical,

,(c) a halogen atom,

(d) an amino radical including substituted as well as unsubstitutedamino radicals such as an alkylamino or a phenylalkylamino radical,

(e) an alkoxy radical,

(f) a hydroxy radical,

(g) a cyano radical,

(h) a heterocyclic radical such as a pyrazolyl, a carbazolyl or apyridyl radical;

or (2) tetra-substituted hydrazines containing substituents which aresubstituted or unsubstituted phenyl radicals, or heterocyclic radicalshaving 5 to 6 atoms in the hetero nucleus, suitable results beingobtainedwhen all four substituents are not unsubstituted phenylradicals, i.e., if at least one substituent is a substituted phenylradical or a heterocyclic radical having 5 to 6 atoms in the heteronucleus. Other tetra-substituted hydrazines include those having thefollowing formula:

wherein D E G and I are each either (a) a substituted phenyl radicalsuch as a naphthyl radical, an alkylphenyl radical, a halophenylradical, a hydroxyphenyl radical, a haloalkylphenyl radical or ahydroxyalklphenyl radical or (b) a heterocclic radical such as animidazolyl radical, a

furyl radical or a pyrazolyl radical. In addition, 1 and E can also be,(c) an unsubstituted phenyl radical. Especially preferred are thosetetra-substituted hydrazines wherein both D and G are either substitutedphenyl radicals or heterocyclic radicals. These compounds are more fullydescribed in U.S. Ser. No. 673,962 filed Oct. 9, 1967.

(G) Organic compounds having a 3,3'-bis-aryl-2-pyrazoline nucleus whichis substituted in either five-member ring with the same or difierentsubstituents. The 1 and 5 positions on both pyrazoline rings can besubstituted by an aryl moiety including unsubstituted as well assubstituted aryl substituents such as alkoxyaryl, alkaryl, alkaminoaryl,carboxyaryl, hydroxyaryl and haloaryl. The 4 position can containhydrogen or unsubstituted as well as substituted alkyl and aryl radicalssuch as alkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl,alkoxyalkyl, amonoalkyl, carboxylaryl, hydroxyalkyl and haloalkyl.

Other photoconductors in this class are represented by the followingstructure:

wherein:

D D' I and J can be either a phenyl radical including a substitutedphenyl radical such as a tolyl radical or a naphthyl radical including asubstituted naphthyl radical,

E E G G' L and U can be any of the substituents set forth above and inaddition can be either a hydrogen atom or an alkyl radical containing1-8 carbon atoms. These organic photoconductors are more fully describedin U.S. Ser. No. 664,642, filed Aug. 31, 1967.

(H) Triarylamines in which at least one of the aryl radicals issubstituted by either a vinyl radical or a vinylene radical having atleast one active hydrogen-containing group. The phrase vinylene radicalincludes substituted as well as unsubstituted vinylene radicals and alsoincludes those radicals having at least one and as many as tlneerepeating units of vinylene groups such as {-CH=CH- wherein n in aninteger of from one to three. Groups which contain active hydrogen arewell known in the art, the definitions of this term being set forth inseveral textbooks such as Advanced Organic Chemistry, R. C. Fuson, pp.154-157, John Wiley & Sons, 1950. The term active hydrogen-containinggroup as used herein includes those compounds encompassed by thediscussion in the textbook cited above and in addition includes thosecompounds which contain groups which are hydrolyzable to activehydrogen-containing groups. Typical active hydrogen-containing groupssubstituted on the vinylene radical of the triarylamine include:

(a) carboxy radicals, (b) hydroxy radicals, (c) ethynyl radicals, (d)ester radicals (e.g.,

o I] C-O R13 wherein R is alkyl or aryl) including cyclic ester radicals(e.g.,

wherein R is a cyclic alkylene radical connected to a vinylenecombination such as is found' in coumarin derivatives),

(e) carboxylic acid anhydride radicals,

(f) semicarbazono radicals,

(g) cyano radicals,

(h) acyl halide radicals (e.g.,

if CCl etc.

and (i) amido radicals (e.g.,

R15 ll ---:O-N

wherein R is a hydrogen atom, an alkyl group or an aryl group).

Other active hydrogen-containing groups include substituted andunsubstituted alkylidyne oximido radicals.

Photoconductors included in this class can be represented by thefollowing structure:

(a) Ar and Ar are each a phenyl radical including a substituted phenylradical such as a halophenyl radical, an alkyl phenyl radical or anaminophenyl radical;

(b) Ar is an arylene radical including a substituted arylene radicalsuch as a phenylene radical or a naphthylene radical,

(c) R and R are each hydrogen, a phenyl radical including a substitutedphenyl radical or a lower alkyl radical preferably having 1-8 carbonatoms;

(d) X is either (1) an active hydrogen-containing group such as acarboxy radical, an acyl halide radical, an amido radical, a carboxylicacid anhydride radical, an ester radical, a cyano radical, a hydroxyradical, a semicarbazono radical, an ethynyl radical, or a methylidyneoximido radical, or (2) hydrogen, provided that when X is hydrogen R andR are also hydrogen; and

(e) n is an integer of one to three.

wherein:

The arylene nucleus can be substituted in any position by the vinyl orvinylene moiety. However, when Ar is phenylene, particularly goodresults are obtained if the substitution occurs in the para position.These materials are more fully described in U.S. Ser. No. 706,800, filedFeb. 20, 1968.

(I) Triarylamines in which at least one of the aryl radicals issubstituted by an active hydrogen-containing group. The term activehydrogen-containing group has the same meaning as set forth above andagain includes those compounds encompassed by the discussion in thetextbook and additionally includes those compounds which contain groupswhich are hydrolyzable to active hydrogen-containing groups. Typicalactive hydrogen-containing groups which are substituted on an arylradical of the triaryl- 4 amine include:

(a) carboxy radicals; (b) hydroxy radicals; (c) ethynyl radicals; (d)ester radicals (e.g.,

etc.

(j) amido radicals (e.g.,

Rm wherein R is a hydrogen atom, an alkyl group or an y p);

(k) lower alkylidyne oximido radicals having 1-8 carbon atoms includingsubstituted alkylidyne oximido radicals wherein R is hydrogen or a loweralkyl radical); (l) semicarbazono radicals; and

(m) arylene carboxy radicals including substituted arylene carboxyradicals e.g.,

wherein D and E are phenyl or lower alkyl radicals.

Photoconductors included in this class can be represented by thefollowing structure:

wherein:

(a) Ar, and Ar are each a phenyl radical including a substituted phenylradical such as a halophenyl radical, an alkyl phenyl radical or anamino phenyl radical;

(b) Ar is an arylene radical including a substituted arylene radicalsuch as a phenylene radical or a naphthylene radical; and

(c) X is an active hydrogen-containing group such as a carboxy radical,an acyl halide radical, an amido radical, a carboxylic acid anhydrideradical, an ester radical, a cyano radical, a semicarbazono radical, ahydroxy radical, an ethynyl radical, a methylidyne oximido radical or aphenylene carboxy radical. These materials are more fully described inUS. Ser. No. 706,780, filed Feb. 20, 1968.

(J Organo-metallic compounds having at least one amino-aryl substituentattached to a Group IVa or Group Va metal atom. The metallicsubstituents of this class of organic photoconductors are Group IVa orGroup Va metals in accordance with the Periodic Table of the Elemerits(Handbook of Chemistry and Physics, 38 edition, pp. 394-) and includesilicon, germanium, tin and lead from Group IVa and phosphorus, arsenic,antimony and and bismuth from Group Va. These materials can besubstituted in the metallo nucleus with a wide variety of substituentsbut at least one of the substituents must be an amino-aryl radical. Theamino radical can be positioned anywhere on the aromatic nucleus, butbest results are obtained if the aryl moiety is a phenyl radical havingthe amino group in the 4 or para position. Typical substituents attachedto the metal nucleus include the following:

Photoconductors included in this class can be represented by thefollowing structures:

l s T-Ar-AIAFD where E G L and Q can be (a) a hydrogen atom,

(b) an aryl radical including unsubstituted as well as substituted arylradicals such as a phenyl radical, a naphthyl radical, adialkylaminophenyl radical, or a diarylaminophenyl radical,

(c) an alkyl radiwl having 1 to 8 carbon atoms,

(d) an alkoxy radical having 1 to 8 carbon atoms,

(e) an aryloxy radical such as a phenoxy radical,

(f) an amino radical having the formula wherein R and R can be hydrogenatoms or alkyl radicals having 1 to 8 carbon atoms, or (g) aheterocyclic radical having 5 to 6 atoms in the hetero nucleus includingat least one nitrogen atom such as a triazolyl, a pyridyl radical, etc.;

T is an amino radical such as an alkylamino radical having 1 to 8 carbonatoms or an arylamino radical such as a phenylamino radical;

Ar is an aromatic radical such as phenyl or naphthyl;

M and M are the same or diiferent Group IVa metals;

M is a Group Va metal;

D can be any of the substituents set forth above for E G L and Q and inaddition can be a Group IVa organo-metallic radical or when taken withB, an oxygen atom or a sulfur atom;

1 can be any of the substituents set forth above for E G L and Q and inaddition can be when taken with E, an oxygen atom or a sulfur atom.These materials are described in US. Ser. No. 650,664, filed July 3,1967.

(K) Any other organic compound which exhibits photoconductive propertiessuch as those set forth in Australian Pat. 248,402.

Representative organic photoconductors useful in this invention includethe compounds listed below:

TABLE I diphenylamine dinaphthylamine N,N'-diphenylbenzidineN-phenyll-naphthylamine N-pheny1-2-naphthy1amineN,N'-diphenyl-p-phenylenediamine2-carboxy-S-chloro-4'-methoxydiphenylamine p-anilinophenolN,N-di-2-naphthyl-p-phenylenediamine 4,4'-benzylidene-bis-(N,N-dimethyl-m-toluidine triphenylamineN,N,N',N'-tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine4-hexanoyltripheny1amine 4-lauroyltriphenylamine 4hexyltriphenylamine4-dodecyltriphenylamine 4,4'-bis (diphenylamino) benzil 4,4-bis(diphenylamino) benzophenone poly [N,4"- (N,N,N-triphenylbenzidine)polyadipyltriphenylamine 1 0 polysebacyltriphenylaminepolydecamethylenetriphenylamine poly-N- (4-vinylphenyl) diphenyl aminepoly-N- (vinylphenyl) -oc, a'-dinaphthylarnine 4,4'-benzylidine-bisN,N-diethyl-'m-toluidine4',4"-diamino-4-dimethylamino-2,2"-dimethyltriphenylmethane 4,4"-bis(diethylamino -2,6-dichloro-2',2" -dimethyltriphenylmethane 4',4"-bisdiethylamino) -2,2"-dimethyldiphenylnaphthylmethane2',2"-di1nethyl-4,4',4"-tris(dimethylamino) triphenylmethane 4',4-bisdiethylamino -4-methylarnino-2',2"-dimethyltriphenylmethane 4',4"-bisdiethylamino) -2-chloro-2,2"- dimethyl-4- dimethylaminotriphenyhnethane4',4"-bis diethylamino) -4-dimethylamino-2,2',2-trimethyltriphenylmethane 4',4"-bis (dimethylamino-2-chloro-2',2"-dimethyltriphenylmethane 4',4"-bis (dimethylamino-2',2"-dimethyl-4-methoxytriphenylmethane bis 4-diethyl amino) l 1l-triphenylethane bis (4-diethylamino tetraphenylmethane 4,4"-bisbenzylethylamino -2',2"-dimethyltripheny1- methane 4',4-bis(diethylamino) -2',2' '-diethoxytriphenylmethane4,4'-bis(dimethylamino)-1,1, l-triphenylethane 1-(4-N,N-dimethylaminophenyl) -1,1-diphenylethane4dimethylaminotetraphenylmethane 4-diethylaminotetraphenylmethane4,4'-bis(diphenylamino) chalcone 4-diphenylamino-4'-dimethylaminochalcone 4-dimethylarnino-4'-diphenylaminochalcone 4,4'-bis dimethylaminochalcone 4,4-bis (diethyl amino chalcone 4-diethylamine-4'-diphenylaminochalcone 4,4-bis (n-amyloxy) chalcone 4,4'-bis (nitro chalcone4-diphenylaminocha1cone 4-dimethylaminochalcone 4-diphenylaminochalcone4'-dimethylaminochalcone bis- [S-(SH-dibenzo [a,d] cycloheptenyl) ]ether1 S-hydroxy-SH-dib enzo [a,d] cycloheptene 1-{5- (SH-dibenzo [a,d]cycloheptenyl }-4,5-dicarbomethoxy-1,2,3 -triazole 1-{S-(5H-dibenzo[a,d]cycloheptenyl) }-4,5-dibenzoyl 1,2,3-triazo1e 5-azido-5H-dib enzo [a,d]cycloheptene 1-{5- 10,1 l-dihydro-SH-dibenzo [a,d] cycloheptenyl) 4,5-dicarbomethoxy-1 ,2,3-tri azole 1-{5-(10,1l-dihydro-SH-dibenzo[a,d]cycloheptenyl)}- 4,5-dibenzoyl-l ,2,3-1Iiazole4- 5- SH-dibenzo [a,d] cycloheptenyl) ]-N,N-dimethyl anilineN,N-diethyl-3-methyl-4 5 (5 H-dibenzo [a,d] cycloheptenyl) aniline4-[5-(5H-dibenzo[a,d]cyc1oheptenyl) ]-1-dimethylaminonaphthaleneN,N-diethyl-3 methyl-4- 5-( 10,1 l-dihydro-SH-dibenzo [a,d]-cycloheptenyl)] aniline 3 4-dimethylaminophenyl -1, 3,5-cycloheptatriene 3- 4-diethylamino-Z-methylphenyl) -1,3,S-cycloheptatriene 3- 4-dirnethylaminonaphthyl) -1, 3 ,5-cycloheptatriene N,N-diethy1-3 -methy1-4-[5-(5H-dibenzo [a,d]cycloheptenyl) aniline tetra-a-naphthylhydrazine tetra(3-methyl-4-hydroxyphenyl) hydrazine tetra m-hydroxyethylphenyl hydrazinetetra (Z-methyl-S-chloroethylphenyl hydrazine tetra(Z-methyI-S-hydroxyphenyl) hydrazine tetra( l-imidazolyl hydrazineN,N-di-a-naphthyl-N,N'-di 3-methyl-4-hydroxyphenyl) hydrazineN-3-furyl-N-(2-methyl-4-hydroxyphenyl)-N,N-di- 3- naphthylhydrazinetetra-fl-naphthylhydrazine N,N'-di-B-naphthyl-N,N'-diphenylhydrazinetetra-4-t0lylhydrazine N,N'-diphenyl-N,N'-di 3-methyl-4-hydroxyphenyl)hydrazine N,N'-diphenyl-N,N'-di-p-chlorophenylhydrazine phenyltri-2-methyl-5-hydroxyphenyl) hydrazine N,N'-bicarbazylcyclotetrakis(3,9-carbazolylene)6-(3-carbazolyl)-cyclotetrakis(3,9-carbazolylene) 6-(9-carbazolyl)-cyclotetrakis(3,9-carbazolylene)3,3'-bis(3-carbazolyl)-9,9-bicarbazolyl3(3-carbazolyl)-9-(9-carbazolyl)carbazole 3-(9-carbazolyl)-9,9-bicarbazolyl 3,3'-diethyl-9,9-bicarbazolyl3,3'-diphenyl-9,9-bicarbazolyl 3,3'-dichloro-9,9'-bicarbazolyl4,4'-bis(diethylamino)-9,9-bicarbazolyl 3,3-diethxy-9,9'-bicarbazolyl1,1-dihydroxy-9,9-bicarbazolyl 2,2-dicyano-9,9-bicarbazolyltetra(p-diethylaminophenyl) hydrazine 3,3-bis(1,S-diphenyl-Z-pyrazoline)3,3-bis(1-p-tolyl-5-phenyl-2-pyrazoline)3,3'-bis(1,5-[l-naphthyl1-2-pyrazoline)1,5-diphenyl-3-[3-(1-p-tolyl-5-phenyl)-2-pyrazolyl] -2- pyrazoline 3,3-bis( 1,5 -diphenyl-4,5 -dimethyl-2-pyrazoline 3,3 '-bis( 1,4,5-triphenyl-2-pyrazoline 3 ,3 '-bis( 1,5-di-p-tolyl-4-methoxy-Z-pyrazoline) 3,3-bis(l,5-diphenyl-4-dimethylamino-2-pyrazoline) 3,3'-bis[1,5-diphenyl-4-(p-chlorophenyl)-2-pyrazoline] 3,3'-bis[1,5-diphenyl-4,5-di-(p-diethylaminophenyl)-2- pyrazoline] 3,3'-bis[1,5-diphenyl-4-(p-methoxyphenyl)-5-ethy1-2- pyrazoline] 3 ,3'-bis( 1,5 -diphenyl-4-chloromethyl-2-pyrazoline) 1,5 -diphenyl-4,5-dimethyl-3- 3 l-p-tolyl-4'-diethyl- 5,5 '-methylphenyl) -2'-pyrazolyl]-2-pyrazoline 4-( p-dipheny1aminophenyl)-3 -buten-l-ynep-diphenylaminostyrene ethyl p-diphenylaminocinnamate methylp-diphenylaminocinnamate p-diphenylaminocinnamoyl chloridep-diphenylaminocinnamic acid N,N-diphenylamide p-diphenylaminocinnamicacid anhydride 3-(p-diphenylaminophenyl)-2-butenoic acid bis(p-diphenylarninobenzal succinic acid4-N,N-bis(p-bromophenyl)aminocinnamic acid1-(4-diphenylamino)naphthacrylic acid p-diphenylaminocinnamic acidp-diphenylaminocinnamonitrile 7-diphenylamino coumarinp-diphenylarninophenylvinylacrylic acid p-diphenylaminobenzylp-diphenylaminocinnamate 7-( p-diphenylaminostyryl coumarinp-diphenylaminocinnamyl alcohol 4-diphenylaminocinnamaldehydesemicarbazone O-p-diphenylatninocinnamoyl p'-diphenylaminobenzaldehydeoxime p-diphenylaminocinnamaldehyde oxime1,3-bis(p-diphenylaminophenyl)-2-propen-l-ol methylp-diphenylaminobenzoate N,N-diphenylanthranilic acid3-p-diphenylarninophenyl-1-propanol 4-acetyltriphenylamine semicarbazoneethyl 2,6-diphenyl-4-(p-diphenylaminophenyl)benzoate 1-(p-diphenylaminophenyl -1 -hydroxy-3 -butyne4-hydroxymethyltriphenylamine 1-(p-diphenylaminophenyl)ethanol4-hydroxytriphenylamine 12 Z-hydroxytriphenylamine4-formyltriphenylamino oxime 4-acetyltriphenylamine oximel-(p-diphenylaminophenyl)hexanol l-p-diphenylaminophenyl)dodecanolp-diphenylaminobenzoic acid anhydride 4-cyanotriphenylaminep-diphenylarninobenzoic acid N,N-diphenylamide p-diphenylaminobenzoicacid p-diphenylaminobenzoyl chloride 3-p-diphenylaminophenylpropionicacid 4-formyltriphenylamine semicarbazonetriphenyl-p-diethylaminophenylsilanemethyl-diphenyl-p-diethylaminophenylsilanetriphenyl-p-diethylaminophenylgermanetriphenyl-p-dimethylaminophenylstannanetriphenyl-p-diethylaminophenylstannane diphenyl-di-(p-diethylaminophenylstannane triphenyl-p-diethylaminophenylplumbanetetra-1rdiethylaminophenylplumbanephenyl-di-(p-diethylaminophenyl)phosphinebis(p-diethylaminophenyl)phosphine oxide tri-p-dimethylaminophenylarsinetri-p-diethylaminophenylarsine 2-methyl-4-dimethylaminophenylarsineoxide tri-p-diethylaminophenylbisrnuthine methyl-di-(p-diethylaminophenyl) arsine methyl-di-p-diethylaminophenyl)phosphinephenyl-tri(p-diethylaminophenyl)stannane methyl-tri(p-diethylaminophenyl) stannane tetra-p-diethylaminophenylgermanediphenyl-p-diethylarninophenylsilane p-diethylaminophenylarsinetetrakis- [diphenyl- (p-diethylarninophenyl plumbyl] methane tetrakis-[diphenylp-diethylaminophenyl) stannyl] stannane bis- [phenyl-(p-diethylaminophenyl) 1 dibismuthinetri-(p-diethylaminophenyl)phosphine sulfidedi-(p-diethylarninophenyl)thioxotin The photoconductive layers of theinvention can also be sensitized by the addition of elfective amounts ofsensitizing compounds to exhibit improved electrophotosensitivity.Sensitizing compounds useful with the photoconductive compounds of thepresent invention can be selected from a wide variety of materials,including such materials as pyrylium including thiapyrylium andselenapyrylium dye salts disclosed in Van Allan et al. US. Pat.3,250,615; fiuorenes, such as 7,12-dioxo-13-dibenzo(a,h) fiuorene,5,15-dioxo4a,11-diazabenzo(b)fluorene, 3,13-dioxo-7-oxadibenzo(b,g)fluorene, and the like; aromatic nitro compoundsof the kinds described in US. Pat. 2,- 610,120; anthrones like thosedisclosed in US. Pat. 2,670,- 284; quinones, US. Pat. 2,670,286;benzophenones US. Pat. 2,670,287; thiazoles US. Pat. 2,732,301; mineralacids; carboxylic acids, such as maleic acid, dichloroacetic acid, andsalicyclic acid; sulfonic and phosphoric acids; and various dyes, suchas cyanine (including cartbocyanine), merocyanine, diarylmethane,thiazine, azine, oxazine, xanthene, phthalein, acridine, azo,anthraquinone dyes and the like and mixtures thereof. The sensitizerspreferred for use with the compounds of this invention are selected frompyrylium salts including selenapyrylium and thiapyrylium salts, andcyanine dyes including carbocyanine dyes.

Where a sensitizing compound is employed with the binder and organicphotoconductor to form a sensitized electrophotographic element, it isthe normal practice to mix a suitable amount of the sensitizing compoundwith the coating composition so that, after thorough mixing, thesensitizing compound is uniformly distributed in the coated element.Other methods of incorporating the sensitizer or the effect of thesensitizer may, however, be employed consistent with the practice ofthis invention. In

preparing the photoconductive layers, no sensitizing compound isrequired to give photoconductivity in the layers which contain thephotoconducting substances, therefore, no sensitizer is required in aparticular photoconductive layer. However, since relatively minoramounts of sensitizing compound give substantial improvement in speed insuch layers, the sensitizer is preferred. The amount of sensitizer thatcan be added to a photoconductor-incorporating layer to give elfectiveincreases in speed can vary widely. The optimum concentration in anygiven case will vary with the specific photoconductor and sensitizingcompound used. In general, substantial speed gains can be obtained wherean appropriate sensitizer is added in a concentration range from about0.0001 to about 30 percent by weight based on the weight of thefilm-forming coating composition. Normally, a sensitizer is added to thecoating composition in an amount by weight from about 0.005 to about 5.0percent by weight ofthe total coating composition.

ISolvents useful for preparing coating compositions with the binders ofthe present invention can include a wide variety of organic solvents forthe components of the coating composition. For example, benzene;toluene; acetone; Z-butanone; chlorinated hydrocarbons such as methylenechloride; ethylene chloride; and the like; ethers, such astetrahydrofuran and the like, or mixtures of such solvents canadvantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the binders disclosedherein useful results are obtained where the photoconductive substanceis present in an amount equal to at least about 1 weight percent of thecoating composition. The upper limit in the amount of photoconductivematerial present can be widely varied in accordance with usual practice.It is normally required that the photoconductive material be present inan amount ranging from about 1 weight percent of the coating compositionto about 99 weight percent of the coating composition. A preferredweight range for the photoconductive material in the coating compositionis from about weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support canvary widely. Normally, a wet coating thickness in the [range of about0.001 inch to about 0.01 inch is useful in the practice of theinvention. A preferred range of coating thickness is from about 0.002inch to about 0.006 inch before drying although such thicknesses canvary widely depending on the particular application desired for theelectrophotographic element.

Suitable supporting materials for coating the photoconductive layers ofthe present invention can include any of the electrically conductingsupports, for example, paper (at relative humidity above 20 percent);aluminum-paper laminates; metal foils, such as aluminum foil, zinc foil,etc.; metal plates, such as aluminum, copper, zinc, brass, andgalvanized plates; vapor deposited metal layers such as silver, nickelor aluminum on conventional film supports such as cellulose acetate,poly(ethylene terephthalate), polystyrene and the like conductingsupports.

An especially useful conducting support can be prepared by coating atransparent film support material such as poly(ethylene terephthalate)with a layer containing a semiconductor dispersed in a resin. A suitableconducting coating can be prepared from the sodium salt of acarboxyester lactone of a maleic anhydride-vinyl acetate copolymer,cuprous iodide and the like. Such conducting layers and methods fortheir optimum preparation and use are disclosed in U.S. 3,007,901.3.245.833 and 3.267.- 807.

The compositions of the present invention can be employed inphotoconductive elements useful in any of the well knownelectrophotographic processes which require photoconductive layers. Onesuch process is the xerographic process. In a process of this type, anelectrophotographic element held in the dark, is given a blanketelectrostatic charge by placing it under a corona discharge to give auniform charge to the surface of the photoconductive layer. This chargeis retained by the layer owing to the substantial dark insulatingproperty of the layer, i.e., the low conductivity of the layer in thedark. The electrostatic charge formed on the surface of thephotoconductive layer is then selectively dissipated from the surface ofthe layer by imagewise exposure to light by meansof a conventionalexposure operation such as for example, by a contact-printing technique,or by lens projection of an image, or reflex or bireflex techniques andthe like, to thereby form a latent electrostatic image in thephotoconductive layer. Exposing the surface in this manner forms apattern of electrostatic charge by virtue of the fact that light energystriking the photoconductor causes the electrostatic charge in the lightstruck areas to be conducted away from the surface in proportion to theintensity of the illumination in a particular area.

The charge pattern produced by exposure is then developed or transferredto another surface and developed there, i.e., either the charge oruncharged areas rendered visible, by treatment with a medium comprisingelectrostatically responsive particles having optical density. Thedeveloping electrostatically responsive particles can be in the form ofa dust, or powder and generally comprise a pigment in a resinous carriercalled a toner. A preferred method of applying such a toner to a latentelectrostatic image for solid area development is by the use of amagnetic brush. Methods of forming and using a magnetic brush tonerapplicator are described in the following U.S. patents: 2,786,439;2,786,440; 2,786,441 2,811,465; 2,874,- 063; 2,984,163; 3,040,704;3,117,884; and reissue Re. 25,- 779. Liquid development of the latentelectrostatic image may also be used. In liquid development thedeveloping particles are carried to the image-bearing surface in anelectrically insulating liquid carrier. Methods of development of thistype are widely known and have been described in the patent literature,for example, U.S. Pat. 2,297,691 and in Australian Pat. 212,315. In drydevelop ing processes the most widely used method of obtaining apermanent record is achieved by selecting a developing particle whichhas as one of its components a low-melting resin. Heating the powderimage then causes the resin to melt or fuse into or on the element. Thepowder is, therefore, caused to adhere penmanently to the surface of thephotoconductive layer. In other cases, a transfer of the charge image orpowder image formed on the photoconductive layer can be made to a secondsupport such as paper which would then become the final print afterdeveloping and fusing or fusing respectively. Techniques of the typeindicated are well known in the art and have been described in a numberof U.S. and foreign patents, such as U.S. Pats. 2,297,691 and 2,551,582,and in RCA Review, vol. 15 (1954) pages 469-484.

The compositions of the present invention can be used inelectrophotographic elements having many structural variations. Forexample, the photoconductive composition can be coated in the form ofsingle layers or multiple layers on a suitable opaque or transparentconducting support. Likewise, the layers can be contiguous or spacedhaving layers of insulating material or other photoconductive materialbetween layers or overcoated or interposed between the photoconductivelayer or sensitizing layer and the conducting layer. It is also possibleto adjust the position of the support and the conducting layer byplacing a photoconductor layer over a support and coating the exposedface of the support or the exposed or overcoated face of thephotoconductor with a conducting layer. Configurations differing fromthose contained in the examples can be useful or even preferred for thesame or different application for the electrophotographic element. 9

The following examples are included for a further understanding of thisinvention.

1 EXAMPLE 1 1.5 grams of p-bromacetophenone-formaldehyde resin bindercontaining 0.5 gram of 4,4-benzylidene-bis(N,N- diethyl-m-toluidine)photoconductor and .04 gram of 2,4- bis-(4-ethoxyphenyl) 6(4-n-amyloxystyryl)pyrylium fluoroborate sensitizer are dissolved in15.6 grams of methylene chloride by stirring the solids in the solventfor one hour at room temperature. The resulting solution is hand coatedat a wet coating thickness of 0.004 inch on a conducting layercomprising the sodium salt of a carboxyester lactone, such as describedin U.S. 3,260,706, which in turn is coated on a cellulose acetate filmbase. The coating block is maintained at a temperature of 90 F. Afterdrying, the electrophotographic element is charged under positive coronasource until the surface potential, as measured by an electrometerprobe, reaches about 600 volts. It is then subjected to exposure frombehind a stepped density gray scale to a 3000 K. tungsten source. Theexposure causes reduction of the surface potential of the element undereach step of the gray scale from its initial potential, V to some lowerpotential, V, whose exact value depends on the actual amount of exposurein meter-candle-seconds received by the area. The results of themeasurements are plotted on a graph of surface potential V vs. logexposure for each step. The shoulder speed is the numerical expressionof multiplied by the reciprocal of the exposure in meter-candle-secondsrequired to reduce the 600 volt charged surface potential by 100 volts.The toe speedm is the numerical expression of 10 multiplied by thereciprocal of the exposure in meter-candle-seconds required to reducethe 600 volt charged surface potential to 100 volts. This coating isfound to have a positive 100 v. toe speed of 250 and a shoulder speed of1800.

EXAMPLE 2 Example 1 is repeated except that the element is charged undera negative corona source until the surface potential reaches about 600volts (negative). The shoulder and 100 volt toe speeds are determined inthe same manner as Example 1. In this case, the negative shoulder speedis 1400 and the negative 100 volt toe speed is 120.

EXAMPLE 3 For comparison purposes, Examples 1 and 2 are repeated exceptthat the binder used is an unhalogenated acetophenoneformaldehyde resin.The positive shoulder speed is 1000 and the positive 100 volt toe speedis 45. The negative shoulder speed is 1200 while the negative 100 volttOe speed is 32. In comparing this data with the results of Examples 1and 2 it is seen that the halogenated arylketone-formaldehyde resinsexhibited substantially higher speeds than the unhalogenated resins.

EXAMPLE 4 Coating compositions containing Compounds 1 through 8 areprepared and coated in the manner described in Example I. In a darkenedroom, the surface of each of the photoconductive layers so prepared ischarged ,to a potential of about +600 volts under a corona charger. Thelayer is then covered with a transparent sheet bearing a pattern ofopaque and light transmitting areas and exposed to the radiation from anincandescent lamp with an illumination intensity of about 75meter-candles for 12 seconds. The resulting electrostatic latent imageis developed in the usual manner by cascading over the surface of thelayer a mixture of negatively charged black thermoplastic tonerparticles and glass beads. A good reproduction of the pattern results ineach instance.

The haloarylketone-formaldehyde resins useful as binders forelectrophotographic compositions and elements of this invention areprepared by methods known to those skilled in the art. Generally, theappropriate haloarylketone is condensed with formaldehyde. A typicalpreparation is set forth below.

1 6 EXAMPLE 5 0.6 gram of sodium hydroxide is added to a mixture of 100g. (.50 mole) of p-bromoacetophenone and 60 g. (.75 mole) of 35-40%aqueous formaldehyde in 400 ml. of ethanol. The mixture is stirred atreflux for minutes after which the supernatant liquid is decanted fromthe viscous liquid. The resin is Washed by stirring at reflux with 200ml. of 2:1 ethanol-water for 30 minutes. After decanting the liquid, thewashing operation is repeated. The resin is cooled, ground and dried.Approximately grams of p-bromoacetophenoneformaldehyde resin arerecovered.

The invention has been described in detail with particular reference topreferred embodiments thereof but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

I claim:

1. An electrophotographic element comprising a support having coatedthereon a photoconductive composi tion comprising a photoconductor and abinder comprising a haloarylketone-formaldehyde resin.

2. The electrophotographic element of claim 1 wherein thephotoconductive composition contains a sensitizer for saidphotoconductor.

3. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising an organicphotoconductor and a binder comprising a resin having repeated unitsrepresented by the following structure:

wherein X is a halo-substituted aryl group and R is selected from thegroup consisting of an aryl group,

an alkyl group and hydrogen.

4. The electrophotographic element of claim 3 wherein thephotoconductive composition contains a sensitizer for saidphotoconductor.

5. The electrophotographic element as defined in claim 4 wherein saidsensitizer is selected from the group consisting of cyanine and pyryliumdye salts.

6. The electrophotographic element of claim 3 wherein the binder is ap-bromoacetophenone-formaldehyde resin.

7. The electrophotographic element of claim 3 wherein the binder is am-chloroacetophenone-formaldehyde resin.

8. The electrophotographic element of claim 3 wherein the binder is ap-chloroacetophenone-formaldehyde resin.

9. The electrophotographic element of claim 3 wherein the binder is a3,4-dichloroacetophenone-formaldehyde 1'68111.

10. The electrophotographic element of claim 3 wherein the organicphotoconductor is 4,4'-benzylidenebis-(N,N- diethyl-m-toluidine) 11. Anelectrophotographic element comprising a support having coated thereon aphotoconductive composition comprising from about 1 0 to about 60 weightpercent of 4,4'-'benzylidenebis-(N,N-diethyl-m-toluidine) as an organicphotoconductor, 0.005 to about 5.0 weight percent of a sensitizer forsaid photoconductor and a p-bromoacetophenone-formaldehyde resin binder.

12. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising from about 10 to about60 weight percent of 4,4-benzylidenebis-(N,N-diethyl-m-toluidine) as anorganic photoconductor, 0.005 to about 5.0 weight percent 17 of asensitizer for said photoconductor and am-chloroacetophenone-formaldehyde resin.

13. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising from about 10 to about60 weight percent of 4,4-benzylidenebis-(N,N-diethyl-m-toluidine) as anorganic photoconductor, 0.005 to about 5.0 weight percent of asensitizer for said photoconductor and ap-chloroacetophenone-formaldehyde resin binder.

14. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising from about 10 to about60 weight percent of 4,4-benzylidenebis-(N,N-diethyl-m-toluidine) as anorganic photoconductor, 0.005 to about 5.0 weight percent of asensitizer for said photoconductor and a3,4'-dichloroacetophenoneformaldehyde resin binder.

15. In an electrophotographic process wherein an electrostatic chargepattern is formed on a photoconductive element, the improvementcharacterized in that said photoconductive element has a photoconductivelayer comprising an organic photoconductor and ahaloarylketoneformaldehyde resin binder.

16. A photoconductive composition comprising a photoconductor and ahaloarylketone-formaldehyde resin binder.

17. A photoconductive composition comprising an organic photoconductorand a binder comprising a resin having repeating units represented bythe following structure:

GEORGE F. LESMES, Primary Examiner I. C. COOPER, III, Assistant ExaminerU.S. Cl. X.R.

